[bug #64453] [grohtml] man+IP+UR with empty link text sends state machine into wilderness

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?64453>

                 Summary: [grohtml] man+IP+UR with empty link text sends state
machine into wilderness
                   Group: GNU roff
               Submitter: gbranden
               Submitted: Fri 21 Jul 2023 09:37:30 AM UTC
                Category: Driver grohtml
                Severity: 3 - Normal
              Item Group: Incorrect behaviour
                  Status: Confirmed
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Fri 21 Jul 2023 09:37:30 AM UTC By: G. Branden Robinson <gbranden>
Originally reported by Jakub Wilk as
[https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1018965 Debian #1018965].

Reproducer:


$ cat ATTIC/IP-UR.man 
.TH
.IP 1. 4
.UR https://bar.example
.UE


A workaround is not to leave the text empty, though that is supported (and
used by _groff_'s own man pages, in _grotty_(1) and _pic_(1)).

It won't do to just blindly stick a <td> in front of the link text in this
case:


diff --git a/tmac/an.tmac b/tmac/an.tmac
index 33e88be62..732eb026a 100644
--- a/tmac/an.tmac
+++ b/tmac/an.tmac
@@ -1105,8 +1105,9 @@ contains unsupported escape sequence
 .    \" If there was no link text, format URI as its own link text.  We
 .    \" don't add angle brackets here.
 .    el \{\
+.      an-warn GBR: no URI
 .      if \\n[an*is-output-html] \
-.        nop \X^html:<a href="\\*[an*prefix]\\*[an*hyperlink]">\
+.        nop \X^html:<td><a href="\\*[an*prefix]\\*[an*hyperlink]">\
 \\*[an*hyperlink]</a>^\c
 .      if \\n[an*is-output-terminal] \
 .        nop \X^tty: link \\*[an*prefix]\\*[an*hyperlink]^\


...since that introduces spurious `td` tags into URIs without linked text that
are not in "lists" (indented paragraphs).

My surmise is that the state machine _grohtml_ uses has gotten confused.







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